1) Field of the Invention
This invention relates to isothiazolecarboxylic acid derivatives showing excellent activity against rice blast (Pyricularia oryzae) in rice cultivation, rice blast control agents containing the same as active ingredients, and rice blast control methods applying the control agents.
2) Description of the Related Art
Control of disease and insect damage plays an important role in the cultivation of rice. Rice blast (Pyricularia oryzae) is a particularly serious disease so that a variety of fungicides and control methods have been developed and utilized. These control methods or fungicides are, however, not believed to be fully effective. Indeed, they involve one or more drawbacks still to be overcome, such as the control effects. Certain isothiazolecarboxylic acid derivatives are disclosed to have fungicidal and bactericidal activity in Japanese Patent Publication No. 1995/1968, in which it is described that isothiazole carboxylic acid esters and amine salts show control effects on the tomato disease caused by Xanthomonas vesicatoria, the soybean disease triggered by Uromyces phaseoli var. typica and tobacco wildfire. However, this patent publication makes no mention of their effects on rice blast.
Further, U.S. Pat. No. 3,341,547 (1967) discloses that isothiazolecarboamides have herbicidal effects.
Specific effects for a particular disease, however, cannot be generalized by assuming their effectiveness for other diseases. It has also been demonstrated by known facts or empirical rules that herbicidal effects and the control of a particular disease cannot be discussed in a similar manner. For example, agricultural streptomycin is used against tobacco wildfire and the plant disease caused by Xanthomonas but exhibits absolutely no effects on rice blast. Conversely, isoprothiolane, pyrochelon and the like, which are widely used as rice blast control agents, do not show any effects on other diseases.
Rice blast is a disease which causes severe damage in the paddy field. Various control methods have therefore been attempted to date. Several kinds of chemicals are used these days as fungicides for the control of rice blast. However, they are however insufficient in many aspects such as fungicidal effects.
In general, the effectiveness or ineffectiveness of a fungicide can be tested in vitro. It is easy to investigate the fungicide in an experimental room. This is attributed to the fact that the fungicide acts directly on the corresponding fungus. However, some chemicals which have no fungicidal effects in vitro can control plant diseases. Such indirect effects, however, cannot be tested in vitro in many instance, so that it is not easy to study them.